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* [Linux-kernel-mentees] [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists
@ 2020-01-17 13:25 Amol Grover
  2020-02-12 13:45 ` Corey Minyard
  0 siblings, 1 reply; 4+ messages in thread
From: Amol Grover @ 2020-01-17 13:25 UTC (permalink / raw)
  To: Corey Minyard, Arnd Bergmann, Greg Kroah-Hartman
  Cc: Paul E . McKenney, linux-kernel, Joel Fernandes,
	openipmi-developer, linux-kernel-mentees

intf->cmd_rcvrs is traversed with list_for_each_entry_rcu
outside an RCU read-side critical section but under the
protection of intf->cmd_rcvrs_mutex.

ipmi_interfaces is traversed using list_for_each_entry_rcu
outside an RCU read-side critical section but under the protection
of ipmi_interfaces_mutex.

Hence, add the corresponding lockdep expression to the list traversal
primitive to silence false-positive lockdep warnings, and
harden RCU lists.

Add macro for the corresponding lockdep expression to make the code
clean and concise.

Signed-off-by: Amol Grover <frextrite@gmail.com>
---
v3:
- Remove rcu_read_lock_held() from lockdep expression since it is
  implicitly checked.
- Remove unintended macro usage.
 
v2:
- Fix sparse error
  CHECK: Alignment should match open parenthesis

 drivers/char/ipmi/ipmi_msghandler.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index cad9563f8f48..64ba16dcb681 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -618,6 +618,8 @@ static DEFINE_MUTEX(ipmidriver_mutex);
 
 static LIST_HEAD(ipmi_interfaces);
 static DEFINE_MUTEX(ipmi_interfaces_mutex);
+#define ipmi_interfaces_mutex_held() \
+	lockdep_is_held(&ipmi_interfaces_mutex)
 static struct srcu_struct ipmi_interfaces_srcu;
 
 /*
@@ -1321,7 +1323,8 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
 	 * synchronize_srcu()) then free everything in that list.
 	 */
 	mutex_lock(&intf->cmd_rcvrs_mutex);
-	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
+	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
+				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
 		if (rcvr->user == user) {
 			list_del_rcu(&rcvr->link);
 			rcvr->next = rcvrs;
@@ -1599,7 +1602,8 @@ static struct cmd_rcvr *find_cmd_rcvr(struct ipmi_smi *intf,
 {
 	struct cmd_rcvr *rcvr;
 
-	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
+	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
+				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
 		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
 					&& (rcvr->chans & (1 << chan)))
 			return rcvr;
@@ -1614,7 +1618,8 @@ static int is_cmd_rcvr_exclusive(struct ipmi_smi *intf,
 {
 	struct cmd_rcvr *rcvr;
 
-	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
+	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
+				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
 		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
 					&& (rcvr->chans & chans))
 			return 0;
@@ -3450,7 +3455,8 @@ int ipmi_add_smi(struct module         *owner,
 	/* Look for a hole in the numbers. */
 	i = 0;
 	link = &ipmi_interfaces;
-	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link) {
+	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link,
+				ipmi_interfaces_mutex_held()) {
 		if (tintf->intf_num != i) {
 			link = &tintf->link;
 			break;
-- 
2.24.1

_______________________________________________
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Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists
  2020-01-17 13:25 [Linux-kernel-mentees] [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists Amol Grover
@ 2020-02-12 13:45 ` Corey Minyard
  2020-02-12 21:49   ` Paul E. McKenney
  0 siblings, 1 reply; 4+ messages in thread
From: Corey Minyard @ 2020-02-12 13:45 UTC (permalink / raw)
  To: Amol Grover
  Cc: Paul E . McKenney, Arnd Bergmann, linux-kernel, Joel Fernandes,
	openipmi-developer, linux-kernel-mentees

On Fri, Jan 17, 2020 at 06:55:22PM +0530, Amol Grover wrote:
> intf->cmd_rcvrs is traversed with list_for_each_entry_rcu
> outside an RCU read-side critical section but under the
> protection of intf->cmd_rcvrs_mutex.
> 
> ipmi_interfaces is traversed using list_for_each_entry_rcu
> outside an RCU read-side critical section but under the protection
> of ipmi_interfaces_mutex.
> 
> Hence, add the corresponding lockdep expression to the list traversal
> primitive to silence false-positive lockdep warnings, and
> harden RCU lists.
> 
> Add macro for the corresponding lockdep expression to make the code
> clean and concise.
> 
> Signed-off-by: Amol Grover <frextrite@gmail.com>

After reading everything, I think this is correct, but I would like
Paul's stamp of approval on this.

Thanks,

-corey

> ---
> v3:
> - Remove rcu_read_lock_held() from lockdep expression since it is
>   implicitly checked.
> - Remove unintended macro usage.
>  
> v2:
> - Fix sparse error
>   CHECK: Alignment should match open parenthesis
> 
>  drivers/char/ipmi/ipmi_msghandler.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> index cad9563f8f48..64ba16dcb681 100644
> --- a/drivers/char/ipmi/ipmi_msghandler.c
> +++ b/drivers/char/ipmi/ipmi_msghandler.c
> @@ -618,6 +618,8 @@ static DEFINE_MUTEX(ipmidriver_mutex);
>  
>  static LIST_HEAD(ipmi_interfaces);
>  static DEFINE_MUTEX(ipmi_interfaces_mutex);
> +#define ipmi_interfaces_mutex_held() \
> +	lockdep_is_held(&ipmi_interfaces_mutex)
>  static struct srcu_struct ipmi_interfaces_srcu;
>  
>  /*
> @@ -1321,7 +1323,8 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
>  	 * synchronize_srcu()) then free everything in that list.
>  	 */
>  	mutex_lock(&intf->cmd_rcvrs_mutex);
> -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
>  		if (rcvr->user == user) {
>  			list_del_rcu(&rcvr->link);
>  			rcvr->next = rcvrs;
> @@ -1599,7 +1602,8 @@ static struct cmd_rcvr *find_cmd_rcvr(struct ipmi_smi *intf,
>  {
>  	struct cmd_rcvr *rcvr;
>  
> -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
>  		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
>  					&& (rcvr->chans & (1 << chan)))
>  			return rcvr;
> @@ -1614,7 +1618,8 @@ static int is_cmd_rcvr_exclusive(struct ipmi_smi *intf,
>  {
>  	struct cmd_rcvr *rcvr;
>  
> -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
>  		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
>  					&& (rcvr->chans & chans))
>  			return 0;
> @@ -3450,7 +3455,8 @@ int ipmi_add_smi(struct module         *owner,
>  	/* Look for a hole in the numbers. */
>  	i = 0;
>  	link = &ipmi_interfaces;
> -	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link) {
> +	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link,
> +				ipmi_interfaces_mutex_held()) {
>  		if (tintf->intf_num != i) {
>  			link = &tintf->link;
>  			break;
> -- 
> 2.24.1
> 
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists
  2020-02-12 13:45 ` Corey Minyard
@ 2020-02-12 21:49   ` Paul E. McKenney
  2020-02-13 13:04     ` Corey Minyard
  0 siblings, 1 reply; 4+ messages in thread
From: Paul E. McKenney @ 2020-02-12 21:49 UTC (permalink / raw)
  To: Corey Minyard
  Cc: Arnd Bergmann, linux-kernel, Joel Fernandes, openipmi-developer,
	linux-kernel-mentees

On Wed, Feb 12, 2020 at 07:45:52AM -0600, Corey Minyard wrote:
> On Fri, Jan 17, 2020 at 06:55:22PM +0530, Amol Grover wrote:
> > intf->cmd_rcvrs is traversed with list_for_each_entry_rcu
> > outside an RCU read-side critical section but under the
> > protection of intf->cmd_rcvrs_mutex.
> > 
> > ipmi_interfaces is traversed using list_for_each_entry_rcu
> > outside an RCU read-side critical section but under the protection
> > of ipmi_interfaces_mutex.
> > 
> > Hence, add the corresponding lockdep expression to the list traversal
> > primitive to silence false-positive lockdep warnings, and
> > harden RCU lists.
> > 
> > Add macro for the corresponding lockdep expression to make the code
> > clean and concise.
> > 
> > Signed-off-by: Amol Grover <frextrite@gmail.com>
> 
> After reading everything, I think this is correct, but I would like
> Paul's stamp of approval on this.

Acked-by: Paul E. McKenney <paulmck@kernel.org>

But note that I did not trace the locking in the case of ipmi_add_smi().
I did the others, so lockdep can do the last one.  ;-)

							Thanx, Paul

> Thanks,
> 
> -corey
> 
> > ---
> > v3:
> > - Remove rcu_read_lock_held() from lockdep expression since it is
> >   implicitly checked.
> > - Remove unintended macro usage.
> >  
> > v2:
> > - Fix sparse error
> >   CHECK: Alignment should match open parenthesis
> > 
> >  drivers/char/ipmi/ipmi_msghandler.c | 14 ++++++++++----
> >  1 file changed, 10 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> > index cad9563f8f48..64ba16dcb681 100644
> > --- a/drivers/char/ipmi/ipmi_msghandler.c
> > +++ b/drivers/char/ipmi/ipmi_msghandler.c
> > @@ -618,6 +618,8 @@ static DEFINE_MUTEX(ipmidriver_mutex);
> >  
> >  static LIST_HEAD(ipmi_interfaces);
> >  static DEFINE_MUTEX(ipmi_interfaces_mutex);
> > +#define ipmi_interfaces_mutex_held() \
> > +	lockdep_is_held(&ipmi_interfaces_mutex)
> >  static struct srcu_struct ipmi_interfaces_srcu;
> >  
> >  /*
> > @@ -1321,7 +1323,8 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
> >  	 * synchronize_srcu()) then free everything in that list.
> >  	 */
> >  	mutex_lock(&intf->cmd_rcvrs_mutex);
> > -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> > +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> > +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
> >  		if (rcvr->user == user) {
> >  			list_del_rcu(&rcvr->link);
> >  			rcvr->next = rcvrs;
> > @@ -1599,7 +1602,8 @@ static struct cmd_rcvr *find_cmd_rcvr(struct ipmi_smi *intf,
> >  {
> >  	struct cmd_rcvr *rcvr;
> >  
> > -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> > +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> > +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
> >  		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
> >  					&& (rcvr->chans & (1 << chan)))
> >  			return rcvr;
> > @@ -1614,7 +1618,8 @@ static int is_cmd_rcvr_exclusive(struct ipmi_smi *intf,
> >  {
> >  	struct cmd_rcvr *rcvr;
> >  
> > -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> > +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> > +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
> >  		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
> >  					&& (rcvr->chans & chans))
> >  			return 0;
> > @@ -3450,7 +3455,8 @@ int ipmi_add_smi(struct module         *owner,
> >  	/* Look for a hole in the numbers. */
> >  	i = 0;
> >  	link = &ipmi_interfaces;
> > -	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link) {
> > +	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link,
> > +				ipmi_interfaces_mutex_held()) {
> >  		if (tintf->intf_num != i) {
> >  			link = &tintf->link;
> >  			break;
> > -- 
> > 2.24.1
> > 
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [Linux-kernel-mentees] [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists
  2020-02-12 21:49   ` Paul E. McKenney
@ 2020-02-13 13:04     ` Corey Minyard
  0 siblings, 0 replies; 4+ messages in thread
From: Corey Minyard @ 2020-02-13 13:04 UTC (permalink / raw)
  To: Paul E. McKenney
  Cc: Arnd Bergmann, linux-kernel, Joel Fernandes, openipmi-developer,
	linux-kernel-mentees

On Wed, Feb 12, 2020 at 01:49:56PM -0800, Paul E. McKenney wrote:
> On Wed, Feb 12, 2020 at 07:45:52AM -0600, Corey Minyard wrote:
> > On Fri, Jan 17, 2020 at 06:55:22PM +0530, Amol Grover wrote:
> > > intf->cmd_rcvrs is traversed with list_for_each_entry_rcu
> > > outside an RCU read-side critical section but under the
> > > protection of intf->cmd_rcvrs_mutex.
> > > 
> > > ipmi_interfaces is traversed using list_for_each_entry_rcu
> > > outside an RCU read-side critical section but under the protection
> > > of ipmi_interfaces_mutex.
> > > 
> > > Hence, add the corresponding lockdep expression to the list traversal
> > > primitive to silence false-positive lockdep warnings, and
> > > harden RCU lists.
> > > 
> > > Add macro for the corresponding lockdep expression to make the code
> > > clean and concise.
> > > 
> > > Signed-off-by: Amol Grover <frextrite@gmail.com>
> > 
> > After reading everything, I think this is correct, but I would like
> > Paul's stamp of approval on this.
> 
> Acked-by: Paul E. McKenney <paulmck@kernel.org>
> 
> But note that I did not trace the locking in the case of ipmi_add_smi().
> I did the others, so lockdep can do the last one.  ;-)

Thanks, it's in my queue for 5.7.

-corey

> 
> 							Thanx, Paul
> 
> > Thanks,
> > 
> > -corey
> > 
> > > ---
> > > v3:
> > > - Remove rcu_read_lock_held() from lockdep expression since it is
> > >   implicitly checked.
> > > - Remove unintended macro usage.
> > >  
> > > v2:
> > > - Fix sparse error
> > >   CHECK: Alignment should match open parenthesis
> > > 
> > >  drivers/char/ipmi/ipmi_msghandler.c | 14 ++++++++++----
> > >  1 file changed, 10 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> > > index cad9563f8f48..64ba16dcb681 100644
> > > --- a/drivers/char/ipmi/ipmi_msghandler.c
> > > +++ b/drivers/char/ipmi/ipmi_msghandler.c
> > > @@ -618,6 +618,8 @@ static DEFINE_MUTEX(ipmidriver_mutex);
> > >  
> > >  static LIST_HEAD(ipmi_interfaces);
> > >  static DEFINE_MUTEX(ipmi_interfaces_mutex);
> > > +#define ipmi_interfaces_mutex_held() \
> > > +	lockdep_is_held(&ipmi_interfaces_mutex)
> > >  static struct srcu_struct ipmi_interfaces_srcu;
> > >  
> > >  /*
> > > @@ -1321,7 +1323,8 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
> > >  	 * synchronize_srcu()) then free everything in that list.
> > >  	 */
> > >  	mutex_lock(&intf->cmd_rcvrs_mutex);
> > > -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> > > +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> > > +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
> > >  		if (rcvr->user == user) {
> > >  			list_del_rcu(&rcvr->link);
> > >  			rcvr->next = rcvrs;
> > > @@ -1599,7 +1602,8 @@ static struct cmd_rcvr *find_cmd_rcvr(struct ipmi_smi *intf,
> > >  {
> > >  	struct cmd_rcvr *rcvr;
> > >  
> > > -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> > > +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> > > +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
> > >  		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
> > >  					&& (rcvr->chans & (1 << chan)))
> > >  			return rcvr;
> > > @@ -1614,7 +1618,8 @@ static int is_cmd_rcvr_exclusive(struct ipmi_smi *intf,
> > >  {
> > >  	struct cmd_rcvr *rcvr;
> > >  
> > > -	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
> > > +	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link,
> > > +				lockdep_is_held(&intf->cmd_rcvrs_mutex)) {
> > >  		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)
> > >  					&& (rcvr->chans & chans))
> > >  			return 0;
> > > @@ -3450,7 +3455,8 @@ int ipmi_add_smi(struct module         *owner,
> > >  	/* Look for a hole in the numbers. */
> > >  	i = 0;
> > >  	link = &ipmi_interfaces;
> > > -	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link) {
> > > +	list_for_each_entry_rcu(tintf, &ipmi_interfaces, link,
> > > +				ipmi_interfaces_mutex_held()) {
> > >  		if (tintf->intf_num != i) {
> > >  			link = &tintf->link;
> > >  			break;
> > > -- 
> > > 2.24.1
> > > 
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-02-13 13:04 UTC | newest]

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2020-01-17 13:25 [Linux-kernel-mentees] [PATCH v3] drivers: char: ipmi: ipmi_msghandler: Pass lockdep expression to RCU lists Amol Grover
2020-02-12 13:45 ` Corey Minyard
2020-02-12 21:49   ` Paul E. McKenney
2020-02-13 13:04     ` Corey Minyard

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